This invention relates to porcelain insulator type circuit breaker having an insulating tube provided with an interrupting unit and capable of easily removing the unit from the tube, particularly for the inspection of the circuit breaker.
FIG. 1 shows a conventional typical 60 KV-class three-phase porcelain insulator type circuit breaker, in which, in each phase, an interrupting unit is accomodated in an upper porcelain tube 4 mounted on a lower porcelain tube 2 which is secured to a supporting frame 1. In such a prior art circuit breaker, when it is required to remove the interrupting unit 3 from the upper porcelain tube for the inspection thereof, the unit 3 is taken out by firstly opening a head cover 30, removing bolts for securing the unit 3 and lifting the unit from the upper porcelain tube 4 by means of a crane 31 or the like or by lifting and shifting the upper tube 4 to another place and taking out the interrupting unit 3 from the tube 4 at that place.
However, such methods for removing the interrupting unit involve the following problems.
1. A considerably large space is required above the circuit breaker for lifting and removing the interrupting unit therefrom, and particularly, in an indoor installation type, it is necessary to build a considerably tall building. PA1 2. Lifting means such as a crane is needed for lifting the interrupting unit or the upper porcelain tube. PA1 3. A scaffold is required to assist the disassembly of the circuit breaker for the reason that the circuit breaker is mounted on the supporting frame and the upper porcelain tube or the interrupting unit is further lifted upwardly. Furthermore, much caution must be exercised for workers who work at a high position (usually, more than 2 m above the ground surface).
In another example of the prior art, a frame is attached to the lower porcelain tube 2 and on the frame there is provided rails and a carriage movable therealong. In this prior art example, the interrupting unit 3 is removed from the upper porcelain tube 4 in a manner that the upper porcelain tube 4 is shifted on the carriage and moved on the rails and the interrupting unit 3 is then taken out from the lower end of the upper tube 4. However, in such a case, the use of the rails and the carriage and the assembling of these members involves much time and more work and thus is not advantageous.